Autoimmunity results when an organism's natural mechanisms for preventing its immune system from attacking its own cells and tissues break down. Diseases, disorders and conditions caused by breakdown, and by the aberrant self-directed immune responses that result, are referred to as autoimmune diseases. Notable examples of autoimmune diseases, disorders and conditions include diabetes mellitus, systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and some allergies. Autoimmune diseases are estimated to be among the ten leading causes of death. Investment in the development of therapies for autoimmune diseases is in the multi-billion dollar range, and critical in vivo systems to test, develop and validate candidate therapeutics are necessary to ensure treatment safety and effectiveness. Further, such in vivo systems are necessary in determining if new treatments can sustain long term improvement in patients and, perhaps, can even provide cures for many diseases that remain unaddressed. Such in vivo systems also provide a source for assays in human hematopoietic and immune system related functions in vivo, identification of novel therapies and vaccines.